I have found 18" executioners with 110 grain inserts to be a perfect match for my Matrix 310 which is the same as your Grizzly.
I have used Executioners, Spynal Tapps, and Zombies with the Matrix 310 and Matrix 330 with very similar results.
The spynal Tapps and Zombies are a little stiffer than the Executioners, but the Executioners are plenty stiff enough for the Grizzly and are very impressive when it comes to accuracy.